Supporting system with bridging members

ABSTRACT

A supporting system for use between two opposing supports comprised of at least two joists and at least one bridging member. The joists span between the opposing supports and are adjacent to each other. The joists each include bridging holes. The bridging members are between the adjacent joists and the bridging members are adapted to engage the bridging holes in the joists.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This patent application relates to U.S. Provisional Patent ApplicationNo. 60/514,622 filed on Oct. 28, 2003 entitled SINGLE WEB COLD FORMEDJOIST, U.S. patent application Ser. No. 10/721,610 filed on Nov. 25,2003 entitled SEGMENTED COLD FORMED JOIST, U.S. patent application Ser.No. 10/974,964 filed on Oct. 28, 2004 entitled COLD-FORMED STEEL JOISTS,and U.S. patent application Ser. No. 12/461,367 filed on Aug. 10, 2009entitled LOWER CHORD COLD-FORMED STEEL JOISTS and incorporates byreference subject matter of these applications in its entirety herewith.

FIELD OF INVENTION

This invention relates to cold-formed steel joists and to assemblies ofsuch joists to provide structural support for floors and roofs in thebuilding construction industry, such as support including fire ratedsteel-concrete composite structures. Both top chord and bottom chordsupported joists are included as aspects of the said invention.

BACKGROUND OF INVENTION

Joists are commonly used in the construction industry to span a distancebetween opposing walls and provide a structural support for a floor,roof or the like. Joists can be comprised of a variety of materialsincluding softwood, wood based laminates, and metal, particularly steel.

Steel joists can be constructed in an open web configuration, whichgenerally consists of spaced apart upper and lower chord members whichextend longitudinally thereof and are fastened together by a zig-zagweb. Such open web joists are typically manufactured from hot-rolledsteel structural members namely the upper and lower chords and the webs.The webs typically can be comprised of hot-rolled steel rods, which areformed into a zig-zagged pattern and welded to the upper and lowerchords. Integral parts of the web are the end angled supports thatconnect the ends of the lower chord to the upper chord to counter loadstresses at the ends of the joist. Open web joists are normally topchord bearing meaning that they are supported by the underside of thetop chord, so that the top chord extends longitudinally beyond thebottom chord and the end angle supports to provide bearing interfacewith the opposing walls.

Open web joists are by their nature highly customizable in terms oftheir load bearing capabilities. Both chords and the zig-zag web can bemade from different thickness of steel, and the members constituting thezig-zag web can vary in thickness along the length of the joist. Thewebs are open in the sense that there is a space between the rodslongitudinally along the central web section that can receive utilitiessuch as wires, pipe work, air ducts or the like. Open web joists can beconcentric, meaning that the load being supported exerts forces thatsubstantially pass through the centres of gravity of the joists. If thejoists are loaded otherwise, they are termed eccentric.

The joist industry has introduced various types of compositesteel-concrete non-combustible floor and roof systems for theconstruction industry, in which the top chords are embedded into aconcrete slab, such a slab having both load bearing and fire resistantproperties. Examples of composite joists can be found in U.S. Pat. Nos.5,941,035, 4,741,138, 4,454,695 and U.S. Publication No. 2002/0069606A1. A composite joist design permits the top chord member of a joist tobe designed with less steel in comparison with non-composite systemssince the concrete slab when properly bonded to the upper steel joistprovides additional load support for the floor or roof system.

Generally speaking, for a structural joist member to be composite itmust have means to mechanically interlock with the concrete to providesheer bonding. It is generally difficult and costly to design steel andconcrete composite floors using steel joists. Simply affixing verticalstuds to the top chord is forbidden by safety regulations in manyjurisdictions which state that structural members cannot have objectsextending above a structural floor member that will encumber the walkingpath of a worker.

The methods for providing sheer bonding between the joist and theconcrete in a composite joist are generally expensive to produce in theprior art.

Furthermore, camber (defined as a slight arch added to the joist) hasbeen introduced into the open web joist technology to offset thedeflection associated with dead loads such that only the live loaddeflection of the joist needs to be accounted for in designs of thejoist. However large machines or jigs are needed to impart the camber tothe chords of the joist where typically the web resists the camberingprocess.

Moreover, hot-rolled open web joists are typically coated or finishedwith a coloured primer. Steel joists manufacturers typically use largetanks of paint into which completed welded joist assemblies are dippedto receive a coating of primer paint. However, the process has becomemore expensive due to environmental considerations when using dippedtanks containing volatile solvents.

Furthermore construction with open web joists is dependent on skilledlabour which in many instances sets the critical path schedule on manyconstruction projects during busy construction season periods whenskilled labour is in highest demand. Because both the manufacture andusage in construction are labour intensive, open web steel joists arecostly, so that their use is viable only in larger commercial andindustrial structures requiring spans near 40 feet and above.

An alternative approach to the open web steel joist is the cold-formedsteel joist. Cold-formed steel structural designs have been used infloor and roof joists in the building construction trade for some time.However prior art cold-formed steel joists have found limitedapplication due to the high costs of construction assembly, and are notcost effective for span lengths much above 24 feet usage is restrictedto single and multi-family housing, and to commercial low risestructures.

Provided that light gauge steel is used, cost effective mass manufactureof cold-formed steel joists is practical because highly automated coldforming operations such as roll-forming are commercially available.Joists in the prior art are produced by cold-forming a single piece ofsheet metal into a joist comprising a top chord, a web and a bottomchord forming a continuous single structure, and are predominately usedin bottom chord bearing conditions. These joists are generally eccentricin that the load forces do not pass through the centre of gravity of thejoist. The most common example from prior art is the C-shaped joistwhich has a cross sectional profile like the letter C. Other examples ofcold rolled constructions are shown in U.S. Patent Publication Nos.2002/0020138 A1 and 2003/0084637 A1.

Composite fire rated floor structures constructed using cold-formedjoists are commercially available. Examples are Hambro D510 and SpeedFloor both of which have end attachments that are welded, bolted orscrewed onto a single strip cold-formed section to provide a top chordbearing joist. However these provide only limited load capacity due tothe nature of the localized connection of the end attachments to thecold-formed joist member. Further, they are costly to produce.Cold-formed joist manufacturers provide holes longitudinally along thecentral web section that are sized to receive utilities for follow-uptrades. Since cold-formed joist material can be pre-finished (i.e. thecoils of steel can be galvanized or painted) the manufacturing processis less harmful to the worker and environment than the open web coatingprocess described above.

Although cold-formed joists possess superior surface finishes, and canbe mass manufactured in a cost-effective manner because there is verylittle dependency on manpower involved relative to the open web joisttechnology, current state of the art cold-formed joist technology doesnot fully exploit the inherent strength to mass ratio of steel, nor doesit optimize material usage throughout the length of the joist. The samethickness of steel is used in both of the chords and the web, thisthickness being constant along the length of the joist. Eccentricdesigns have a tendency to be unstable under load due to a mechanicalmoment about the longitudinal axis. Consequently substantial bracing isrequired between joists to counteract this effect.

These properties compare unfavourably with the open web steel joistwhere the chords and the web may be of different thickness and the webmember thickness may be varied over the span length in response toloading requirements.

Accordingly, a joist and method of producing said joist that can utilizethe beneficial attributes while avoiding the drawbacks from each of theopen web joist technology and cold-formed joist technology is desirable.Further, it is desirable to manufacture the joist using automatedcold-forming methods as opposed to the labour intensive welding andhandling methods employed in open web steel joist construction. It isalso desirable to have cost effective fire rated composite floors androofs based on cold-formed steel joists integrally attached to aconcrete slab.

Also both open web and cold-formed steel joist floor and roof structuresnormally require bridging systems, comprising steel members spanning thegap between joists in a floor or roof assembly, to stabilize theassembly from any lateral movement or rotational movement about thelongitudinal direction in response to applied loading. It is commonpractice to weld bridging in place between open web joists, whilecold-formed joist systems have bridging structures that commonly usescrews or welding for fastening. Consequently a cost effective means toprovide bridging between joists is highly desirable.

SUMMARY OF THE INVENTION

A supporting system for use between two opposing supports comprised ofat least two joists and at least one bridging member. The joists spanbetween the opposing supports and are adjacent to each other. The joistseach include bridging holes. The bridging member are between theadjacent joists and the bridging members are adapted to engage thebridging holes in the joists.

The joists may include an upper chord, a web and a lower chord. Thebridging holes may be formed in the web. The bridging holes may beformed in at least one of the upper chord and lower chord.

The bridging members may include generally horizontal bridging members.The bridging members may further include criss-crossed bridging memberattached to the generally horizontal bridging members.

The bridging member may be a diaphragm assembly. The diaphragm assemblymay include a steel plate.

The bridging member may further include horizontal bridging members andthe steel plate may be attached to the horizontal bridging members. Thesteel plate may have a hole formed therein.

Each bridging may be adapted to be snapped in place.

The bridging holes are a plurality of spaced apart bridging holes.

The upper chord and lower chord may each include at least one innerflange and the bridging holes may be formed in the inner flanges.

The supporting system may include a plurality of joists and a pluralityof bridging members.

The bridging members include an upper bridging member and a lowerbridging member.

The bridging members may be generally L-shaped.

These and other objects and features of the invention shall now bedescribed in relation to the following drawings:

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a prior art open web steel joist (OWSJ);

FIG. 2 illustrates a prior art cold-formed C-shaped joist;

FIG. 3 illustrates one embodiment of the invention, a concentric topchord bearing segmented web steel joist;

FIG. 4 illustrates segments of a segmented web;

FIG. 5 is a perspective view of a second embodiment of the inventionshowing a concentric top chord bearing, cold-formed joist having threeweb segments;

FIG. 6 is a side elevation view of FIG. 5;

FIG. 7 is a cross sectional view along the line 7-7 of FIG. 5;

FIG. 8 illustrates a side-view of a plurality of joists having bridgingmembers;

FIG. 9 is a side elevation view of a plurality of joists having bothhorizontal bridging and crossed bridging members;

FIG. 10 is a perspective view of a concentric top chord bearingsegmented web cold-formed joist to be used in a composite floor or roofstructure;

FIG. 11 is a side elevation view of FIG. 10;

FIG. 12 is a cross sectional view along the lines 12-12 of FIG. 10 andalso showing a concrete slab attached thereto;

FIG. 13 is a side elevation view of a composite floor system having aplurality of joists;

FIG. 14 and enlargement 14 a are perspective views showing a bottomchord bearing version of another embodiment of the invention;

FIG. 15 is a perspective view showing a top chord bearing version ofanother embodiment of the invention;

FIG. 16 is a cross sectional view of the web only through line 16-16 ofFIG. 6;

FIG. 17 is a cross sectional view of the web only along the line 17-17of FIG. 6;

FIG. 18 is a partial side elevation view of a segmented web;

FIG. 19 is a top view of FIG. 18;

FIG. 20 is a top expanded view of region 20-20 in FIG. 18 showing arivet joining two segments of a web;

FIG. 21 is a partial side elevation view of the reinforcing member 84shown in FIG. 5;

FIG. 22 is a partial view of FIG. 21;

FIG. 23 is a partial top plan view of the reinforcing member;

FIG. 24 is a cross-sectional view of further embodiments of the joistwherein the web and the bottom chord are cold-formed from the same sheetof steel;

FIG. 25 is a cross-sectional view of further embodiments of the joistwherein the web and the bottom chord are cold-formed from the same sheetof steel;

FIG. 26 and enlargement 26 a are perspective views of a bottom chordbearing composite version of another embodiment of the invention;

FIG. 27 is a perspective view of a top chord bearing composite versionof another embodiment of the invention;

FIG. 28 is a schematic view of an automated assembly line for themanufacture of cold-formed joists;

FIG. 29 is a cross section view through the line 116-116 of FIG. 14;

FIG. 30 is a side elevation view of an embodiment of one end of a bottomchord bearing composite cold-formed joist bonded to a concrete slab andintegrated into a side wall;

FIG. 31 is a partial enlarged view of FIG. 30;

FIG. 32 is a cross sectional view through line 112-112 of FIG. 26;

FIG. 33 is a side elevation view of a plurality of another embodiment ofthe invention with horizontal bridging between joists;

FIG. 34 is a side elevation view of a plurality of another embodimentwith diaphragm bridging;

FIG. 35 is a side elevation view of one end of a bottom chord bearingcold-formed joist supported by a foundation wall and supporting a studwall;

FIG. 36 a is a top plan view of the reinforcing flap of FIG. 35;

FIG. 36 b is a perspective view of the reinforcing flap of FIG. 35;

FIG. 37 shows top and plan views of a further reinforcing flap of FIG.35;

FIG. 38 is a bottom chord bearing embodiment of the inventionillustrating the reinforcing end flaps;

FIG. 39 is a side elevation view of FIG. 38; and

FIG. 40 is a cross sectional view of an alternate embodiment of a coldformed joist in a composite floor or roof structure

DETAILED DESCRIPTION OF THE INVENTION

In the description that follows, like parts are marked throughout thespecification and the drawings with the same respective referencenumbers. The drawings are not necessarily to scale and in some instancesproportions may have been exaggerated in order to more clearly depictcertain features of the invention.

FIG. 1 illustrates a prior art open web joist construction 2 consistingof an upper chord assembly 4 spaced from a lower chord assembly 6. Thechords are joined together by a zigzag web 8 which is generallyconnected to the upper and lower chord assemblies 4, 6 by a number ofmeans including welding or the like.

FIG. 2 illustrates a prior art cold formed joist construction 10roll-formed from a single strip of light gauge steel, having a webportion 12 having a plurality of holes 14 disposed therethrough forreceiving utilities such as wire or the like, and having upper and lowerchords 11 and 13 respectively.

FIGS. 3 and 5 illustrate two similar embodiments of the invention,namely top chord bearing concentric joists, which comprise an assembledjoist 20 having a first or upper chord member 22 spaced from a second orlower chord member 24. A steel web member 26 is also disclosed. The webmember 26 is fastened to the upper and lower chord members 22 and 24 byfastening means 28. The fastening means can comprise of a variety offastening means such as bolts and nuts, screws, welding or spot clinches(not shown) or rivets 30 as shown in FIG. 7

The upper and lower chord members 22 and 24 are produced from singlesheets of steel. The joist can be formed in a concentric fashion asshown in FIG. 7 where the upper and lower chord members 22 and 24 aresubstantially symmetrically disposed about web 26.

In these embodiments the upper chord member 22 is cold-formed to presenta substantially flat upper load bearing surface 34 which is formed asshown in FIG. 7 to present lower load bearing wings or extensions 36 and38. The upper load bearing surface 34 is in contact with the lower loadbearing extensions 36 and 38 so as to produce a rigid and structurallysolid member which may be fastened together by the spot clinch 32. Thespot clinch process is conducted in the manner well known to thosepersons skilled in the art and generally consists of a mechanism whichpushes material by a plunger (not shown) to present a mushroomed head 40as shown so as to secure the members together.

The upper load bearing surface 34 and lower load bearing extensions 36and 38 are disposed in this case symmetrically about the web 26, thedirection of which defines the “Y” axis 27 as shown in FIG. 7.Accordingly, the upper load bearing surface 34 in concert with the lowerload bearing extension 36 on one side of the axis 27 defines ahorizontal extension 42 while the upper load bearing surface 34 to theright of the Y axis 27 in concert with the lower load bearing extension38 defines a horizontal extension 44 disposed on the other side of theaxis 27. The lower load bearing extensions 36 and 38 are cold-formedspaced apart web receiving tabs 46 and 48 as shown. The upper portion 50of the web 26 may include a plurality of holes 52 which are adapted toreceive the fastening means 28. FIG. 7 shows an example of a fasteningmeans 28 comprising a rivet 30 that fastens the web 26 to the upperchord 22 at the tabs 46 and 48.

The spot clinches 32 in combination with the cold-formed chords connectthe two folded portions 34 and 36 and 34 and 38 to reduce the width tothickness ratio of the section to avoid local buckling. The spot clinch32 in combination with the cold work forming increases the yieldstrength of the steel part.

As shown in FIG. 7 the lower chord 24 is similarly constructed byforming sheet metal to present a lower chord surface 54 bent so as topresent lower chord extensions 56 and 58 symmetrically disposed aboutaxis 27. The lower chord 54 with the lower chord extensions 56 and 58define lower chord horizontal extensions 60 and 62 in this casesymmetrically disposed about the web 26. The lower chord extensions 56and 58 present two spaced apart web receiving tabs 64 and 66 which areadapted to receive the lower portion 68 of the web 26. The lower chordis also fastened to the lower part of the web 26 by rivets or othermeans

The web 26 can include a plurality of utility holes 72 which provide anaccess for utilities such as electrical wires, air ducts or the like.The holes 72 as shown are circular although any configuration can beproduced including square holes or the like. Furthermore, the holes 72can include a cold-formed lip 74 as shown in FIG. 16. The holes 72lighten the total weight of the joist 20 while the cold-formed lip 74adds rigidity to the web structure 26 particularly in the direction ofthe “Y” axis 27.

The web 26 may also include a plurality of stiffening means 80 tostiffen of the web member 26.

The stiffening means 80 comprises a first stiffening means 82 and asecond stiffening means 84. The first stiffening means 82 generallyconsists of the ends of the web segment 26 being bent to form astiffening tab 82 which is disposed at approximately a 90 degree anglefrom the web 26. The second stiffening means 84 may consist of a hollowembossed rib structure 86 as illustrated in FIG. 21.

The hollow rib structure 86 can be produced by a variety of means and inone example is produced by a punch (not shown) which pushes the webmaterial 26 to present the stiffening structure 84. The stiffeningstructure has two spaced side walls 88 and 90 as well as upper and lowerwalls 92 and 94 and stiffening front wall 96. The stiffening front wall96 has stiffening holes 98 which are adapted to receive bridging members170 and 171 in a manner to be more fully particularized herein.

Furthermore, the web 26 can comprise a plurality of web segments 104,106 and 108, as shown in FIG. 4, in which, as an example, three segmentsare shown. Each of the web segments 104, 106 and 108 are adapted to befastened to one another. In particular, the web segments 104, 106, 108include a first stiffening means 82 which comprise sheet metal flapswhich are bent at substantially 90 degrees from the web material 26. Thefirst stiffening flaps 82 may include a plurality of holes 110 which areadapted to receive fasteners such as rivets, nuts and bolts, or mayreceive spot clinches to secure the plurality of web segments 104, 106,and 108 together to form a web 26. The web segments 104, 106, and 108also include second stiffening means 84, shown in FIG. 3.

The web segments can either all have the same thickness or havedifferent selected thickness. For example the web segments can bethicker at the ends of the joist than segments in the middle of thejoist since the shear stresses under load are greater at the ends thanin the middle.

The joist shown in FIGS. 3 and 5 include angled end support members 140that secure the ends of the lower chord 24 and upper chord 22.

A structural assembly comprising a plurality of joists 20 partiallyshown at FIGS. 8 and 9 can define a supporting surface 160 to support aplatform 162 such as a roof or floor. Each of the joists 20 as shown incross section comprises spaced apart cold-formed steel upper and lowerchord members 22 and 24 and a steel web 26 intermediate between upperand lower chord members 22 and 24. Fasteners 28 are utilised to fastenthe web to the upper and lower chords and the top surface of upperchords 22 define the supporting surface 160.

A plurality of bridging members 170 and 171 may be used to connectadjacent joists 20 together as shown so as to stiffen the said joistassembly. Parallel bridges 170 may be used as shown in FIG. 8, or may beaccompanied by criss-crossed bridges 171 that are appropriately fastenedto the horizontal bridges 170 at 173 as shown in FIG. 9. The fasteningof the bridges 170 to the joists 20 through holes in the embossedfeatures 84 is shown in greater detail in FIGS. 21, 22 and 23,effectively creating a snap in place connection without the use oftools.

The bridge members such as 170 may be formed in an L-shaped crosssection from sheet steel to produce a first surface 172 and a secondsurface 174. The second surface 174 is slotted at 176 as shown and thewidth W of surface 174 is less than the depth D of the hole 98 to permitthe end 178 of the bridging member 170 to be inserted into the hole 98and then rotated so as to lock the edges of the slot 176 against thereinforcement face 96 adjacent the hole 98. Criss-crossed bridgingmembers 171 may then be added and fastened as shown in FIG. 9.

FIGS. 12 and 13 illustrate another embodiment of the invention defininga composite floor or roof structure. In particular, the upper chord 22can be cold-formed so as to present horizontal extensions 190symmetrically disposed about the central web 26 and presents spacedapart vertical extensions 192 and 201 adapted to receive the top portion50 of the web 26 to define a vertical extension 194. A rivet 196 may beutilized to fasten the upper chord 22 to the web 26 as shown.

A steel deck 198 is adapted to rest on the top surface of the horizontalupper chord extensions 190 as shown in FIGS. 12 and 13. A wire mesh 205is added. Thereafter concrete 206 can be poured onto the deck 198 so asto produce a floor or ceiling. Since the vertical extensions 194 areembedded into and bonded with the concrete 200, a very solid compositefloor system is produced. The vertical extension 194 can also include agenerally horizontal concrete engaging extension 202 that runs along thelength of the chord 22. Since the horizontal concrete engaging extension202 runs along the length of the chord 22, the possibility of snagging aworker's foot or clothing is minimized thereby adding to the safetyfeature of the joist prior to pouring of the concrete 206 over the deck198.

The shear bond between the extensions 194 and 202 and the concrete maybe increased by using rivets spot clinches or the like to increase thesurface area of contact between the concrete and the top chord. Despitethe asymmetry provided by the horizontal engaging extension 202, thisembodiment of the joist is substantially concentric since the extensions194 and 202 are bonded to the concrete and the steel-concrete compositeeffectively distributes the applied load to each joist through itscentre of gravity

FIG. 24 illustrates another embodiment of the invention which includesan upper cold-formed steel chord 22 fastened to a steel web 26 byfasteners 30. In the embodiment shown, the bottom chord 24 is acold-formed extension of the web formed so as to present a horizontalextension 250 and 252 which may be of double thickness as shown and maybe hole clinched (not shown) and may be disposed symmetrically orasymmetrically about the plane of the web.

FIG. 25 illustrates another embodiment of the invention, similar thatshown in FIG. 24 where the upper chord 22 has a single layer of sheetmetal which is bent to produce the horizontal extensions 190 spacedapart to accommodate the end 50 of web 26 so as to define an uppervertical extension 194 having a horizontal concrete engaging extension202. The horizontal concrete engaging extension 202 can include aplurality of hole clinches to further strengthen the bond between theconcrete and the upper chord 22 and thereby increase the shear strengthof the composite. Clearly different further embodiments are possiblewherein the bottom chord, being a cold-formed extension of the web, mayhave different forms being symmetric or asymmetric about the web axis,and in parts being of different multiples of the web thickness.

In the following, methods to locate and affix the joist to the opposedsupporting walls are described. The joist 20 can be supported along thebottom chord 24 as shown in FIGS. 30 and 31 illustrating a bottom chordbearing composite joist embodiment 20 supported by the bottom chord 24.

In particular the ends 400 of the joist are disposed within the lowerstud wall 402 and upper stud wall 404 as shown. The lower stud wall 402includes a stud wall track 406 which is generally a flat piece of sheetsteel 408 bent at its ends so as to present a solid surface to thejoist. The upper stud wall 404 includes a similar stud wall track 406.The stud walls 402 and 404 also includes a floor joist track 412adjacent the end 400 of joist 20.

The view of the joist 20 seen in FIG. 30 can have a number ofconfigurations as described in the context of the composite joistincluding that shown in FIG. 12. The composite joist is constructed inthe manner previously described. An erection clip 414 can be utilized soas to locate the joist 20 prior to pouring the concrete to produce thecomposite joist. In particular the erection clip 414 comprises a generalJ-shaped clip in cross-section which is secured to the bottom of thestud wall track 406 and extension 202. Once the concrete 200 is poured,the composite cold formed steel joist is supported by the bottom chord24 at the ends 400 of the joist 20.

FIG. 35, together with the enlargements depicted in FIGS. 36 a and 36 b,illustrates another bottom chord bearing embodiment of the inventionsupported by the foundation walls and supporting the stud walls in aresidential home.

In particular the joist 20 rests on a foundation 401 having a bearingsupport 410. The end 400 of the joist 20 includes a reinforcing flap 82,which provides support against the compressive forces arising from loadsapplied through the stud wall 404, and is further particularized inFIGS. 36 a and 36 b. In particular the flap 82 is cut along cut lines600, 602 and 604 so as to present portions 620 and 622. In particularportions 620 and 622 are folded along fold lines 606 and 608. Thereafterportions 620 and 622 are further folded along fold lines 621 and 623 soas to present wing portions 624 and 626 which are adapted to contactrespectively the lower surface of upper chord member 22 and uppersurface of lower chord member 24 as best shown in FIG. 35. Fasteningmeans may be utilized to fasten the reinforcing wings 624 and 626 toupper and lower chord members 22 and 24 so as to further rigidify andstrengthen the joist 20.

Wooden or metal backing plates 412 are also utilized as shown in FIG.35. Wooden pieces 414 may also be disposed as shown. The upper chord 22provides a support surface for supporting plywood 416 or the like.

Further end reinforcing members 700 may be utilized which comprises anelongated section of sheet metal having web contacting portions 702 andrigidifying portions 704 extending generally perpendicular to the webcontacting portions 702. The ends of the rigidifying portions 704 arebent at 706 and 708 and adapted to contact the upper chord 22 and lowerchord 24 respectively. Furthermore fastening means may be utilized tofasten the rigidifying section 700 to web 26 and upper and lower chords22 and 24.

Moreover FIG. 38 illustrates an embodiment of a bottom chord bearingcold-formed joist utilizing the reinforcing structure 700 shown in FIG.37.

FIG. 28 generally illustrates a method of producing the said embodimentsof the cold-formed joist. The upper chord 22 can be produced byunrolling a coil of sheet steel 112 along path 114 to a roll formingmachine 116 such as sold by Samco machinery located in Toronto, Canada.The roll forming machine 116 can include a station to flatten and cut aselected length of the upper chord member 22. Similarly, the lower chordmember 24 can be produced by unrolling a coil of sheet steel 118 andflattening same along a path 120 to a roll forming machine 116 and thencutting to the desired length. Furthermore, the web 26 can also beproduced by unwinding a coil of sheet steel 122 and flattening same atflattening station 123. A shear 125 can be used to shear the web member26 to its desired length. Thereafter, the web 26 approaches stiffeningsection 128 so as to produce the first and second stiffening means 82and 84 as described.

The shear 125 can be used to produce the plurality of segmented webs104, 106 and 108. Each web segment 104, 106, 108 can have the left handand right hand stiffening flaps 82 produced by stiffening station 130and 132. An appropriate punch 133 is used to produce the secondstiffening means 84 as described above in a drawing operation. As well,punch 133 is used to produce holes 72 and area embossments 184.

The sheet steel at stations 112, 118 and 122 can be galvanized orpainted as desired prior to the forming process. Furthermore the rollforming machine 116 may include punches to punch the appropriate holes52 in the upper and lower chord members 22 and 24 so as to accommodatethe appropriate fastening means 28.

Alternatively the roll forming machine 116 can include apparatus to spotclinch 32 the members together.

Accordingly the joist fabricated herein can be coated with a variety ofpaint colours which are painted prior to fabrication so as to produce avariety of joists having different colours and avoiding the dip paintingcharacteristic of open web joist construction. The invention asdescribed herein presents a number of advantages over the prior art. Forexample, many open web steel joists in the prior art include a camberingof the upper and lower chords 4 and 6 so as to present a slight arch toincrease load bearing capabilities of the joist. Such prior artcambering techniques required working against the web during thecambering process. Applicant's invention on the other hand presents anadvantage since the upper and lower chord members 22 and 24 can becambered individually and separately from the web 26. Once the upper andlower chord members 22 and 24 are cambered they can be attached to theweb 26 as described since the depth of the said camber is adequatelycontained within the web receiving tabs 46, 48 of the upper chord and64, 66 of the lower chord as depicted in FIG. 7. Since the web 26 is notpart of the upper and lower chord members 22 and 24 during the camberingprocess there is substantially less resistance to the cambering.

Alternate versions of the invention are shown in FIGS. 14 and 14 a, FIG.15, FIGS. 29 representing bottom and top chord bearing versions; andFIGS. 26 and 26 a, and FIG. 27, representing bottom and top chordbearing versions of a composite joist. In FIG. 14 and FIG. 29 a topchord 22 and a bottom chord b are attached by web receiving tabs to agenerally planar web 26 that defines a Y-axis 27 of the joist by selfpiercing rivets 30 or other fastening means such as screws or rivets.Said web has longitudinally spaced holes 72 formed therein each with acold-formed lip 74 for increased rigidity under load to allow therouting of pipes, wiring, ductwork and such of other trades. Further webstiffening may be provided by cold-formed area embossments 184 as showndisposed along the length of the web at locations chosen to counteractapplied loads or may be provided by vertical stiffening embossments suchas 84 as previously described. Further stiffening at the ends of thejoist are provided by embossed plates 101 attached by fasteners 130 tothe end portions of the web, and are sized to counter both compressiveand shear stresses near the ends of the joist. Such embossed plates maybe fastened on both sides of each end of the joist, and may terminatelongitudinally in cold-formed flaps 182 that provide increased stiffnessand provide a means of attaching joists at their ends.

As shown in FIG. 29, the construction of the top chord 22 and the bottomchord 24 of this embodiment may be simplified compared with previouslydescribed embodiments. However additional features to those shownpreviously in FIG. 7 say are disclosed. In particular the web receivingtabs 46 and 48 of the top chord are shown extended and cold-formed toprovide outward protruding inner flanges 45 and 47 respectively disposedgenerally orthoganally to the web 26. Said flanges contribute to theoverall strength of the joist; and said flanges are formed with holes198 regularly spaced along the length of the chord and designed toreceive snap-in bridging members as shown in FIGS. 33 and 34. The bottomchord 24 also shows inner flanges 65 and 67 as cold-formed extensions tothe receiving tabs 64 and 66. Without loss of generality, FIG. 29 alsoserves as a cross section view of a top chord bearing version of thisembodiment shown in perspective in FIG. 15

Perspectives of bottom and top chord bearing composite joist versions ofthis embodiment are shown in FIGS. 26, 26 a and FIG. 27, and a crosssection view through line 112-112 is shown in FIG. 32. In FIG. 32, topchord 22 is attached to the web 26 by fastening tabs 192 and 201 ofvertical section 194 by self piercing rivets 196 or other means. Thedouble thickness of steel forming horizontal extension 202 are fastenedby rivets 199 as shown or by other fastening means, with the head ofsaid rivet disposed above the top surface of extension 202 in order toincrease the surface area on the top surface of extension 202 and soenhance shear bonding with concrete. The bottom chord inner flanges 65and 67 are formed with regularly spaced holes 198 to receive snap-inbridging members as shown generally in FIGS. 33 and 34.

An alternate embodiment is shown in FIG. 40 which is similar to theembodiment shown in FIG. 12. In this embodiment the joist 700 onlyincludes a top chord 22 and does not include a web or a bottom chord. Itwill be appreciated by those skilled in the art that this joist wouldonly have application in relatively short spans. Joist 700 includes aconcrete engaging extension 202 which includes a vertical extension 194that extends upwardly from horizontal upper chord extensions 190. Asdescribed above steel deck 198 is adapted to rest on the top surface ofthe horizontal upper chord extensions 190. A wire mesh 205 is added andthereafter concrete 200 is poured onto the deck 198.

A structural assembly comprising a plurality of joists 20 partiallyshown at FIG. 33 can define a supporting surface 160 to support aplatform 162 such as a roof or floor. Each of the joists 20 as shown incross section comprises of spaced cold-formed steel upper and lowerchord members 22 and 24 and a steel web 26 fastened between upper andlower chord members 22 and 24. A plurality of bridging members 170 isused to stiffen the assembly 20, said bridging members being disposedparallel to the support surface; and said flanges may be connected toadjacent joists at the holes 198 provided by the inner flanges 45 and 47of the top chord 22 and by the inner flanges 65 and 67 of the bottomchord 24. Bridging members may be constructed from a length of steel ofangled cross section terminated at each end by a feature 270 that fitsthe holes 198 and allows the bridging member to be snap fastened toinner flanges of adjacent joists.

A further aspect of this invention is illustrated in FIG. 34 partiallyshowing a structural assembly of joists 20 defining a support surface160 supporting a platform 162 such as a floor or roof when both paralleland criss-cross bridging is required. Such combined bridging may beprovided by a diaphragm assembly 370 comprising a steel plate 470affixed by fasteners 670 to upper and lower bridging members 170 eachterminated by a snap-in feature 270 at either end. Said steel plate mayprovide a hole 570 having a cold-formed lip to allow the passage ofwiring, pipes and ducting from other trades. Diaphragm assembly 370providing both parallel and criss-cross bridging may be snap-fastened toadjacent joists by engaging the snap-in feature 270 with the holes 198provided in the inner flanges of the upper and lower chords.

The snap-in bridging illustrated in FIGS. 33 and 34 advances the priorart by substantially reducing the labour and cost involved in the manualassembly of bridging on the construction site. And although FIGS. 33 and34 refer to conventional floor or roof structures, the same bridgingmeans may be used without any loss of generality to the construction ofcomposite steel-concrete floors and roofs.

The support structures described in this invention can be utilizedeither as floor joists or roof joists for single family residential,multi-family residential, commercial or industrial buildingconstruction. Further it will be appreciated by those skilled in the artthat the system described herein may be used as a stay in place formingsystem. Analysis and testing of said structures demonstrate that theprior art is advanced in several regards including:

-   -   more economical bottom chord bearing cold-formed steel joists        with spans up to 40 feet    -   more economical top chord bearing joists capable of mass        manufacture and customization    -   more effective and economical composite floor and roof        structures.

Although the joist embodiments as well as the manufacturing operationsand use in construction have been specifically described in relation tothe drawings, it should be understood that variations in theseembodiments could be achieved by a person skilled in the art withoutdeparting from the spirit of the invention as claimed herein.

As used herein, the terms “comprises” and “comprising” are to beconstrued as being inclusive and opened rather than exclusive.Specifically, when used in this specification including the claims, theterms “comprises” and “comprising” and variations thereof mean that thespecified features, steps or components are included. The terms are notto be interpreted to exclude the presence of other features, steps orcomponents.

It will be appreciated that the above description related to theinvention by way of example only. Many variations on the invention willbe obvious to those skilled in the art and such obvious variations arewithin the scope of the invention as described herein whether or notexpressly described.

1. A supporting system for use between two opposing supports comprising:at least two joists spanning between the opposing supports and adjacentto each other wherein the joists each include bridging holes; and atleast one bridging member between the adjacent joists wherein thebridging members are adapted to engage the bridging holes in the joists.2. The supporting system of claim 1 wherein the joists include a upperchord, a web and a lower chord.
 3. The supporting system of claim 2wherein the bridging holes are formed in the web.
 4. The supportingsystem of claim 2 wherein the bridging holes are formed in at least oneof the upper chord and lower chord.
 5. The supporting system of claim 2wherein the bridging members include generally horizontal bridgingmembers.
 6. The supporting system of claim 5 wherein the bridgingmembers further include criss-crossed bridging member attached to thegenerally horizontal bridging members.
 7. The supporting system of claim2 wherein the bridging member is a diaphragm assembly.
 8. The supportingsystem of claim 7 wherein the diaphragm assembly includes a steel plate.9. The supporting system of claim 8 wherein bridging member furtherincludes horizontal bridging members and the steel plate is attached tothe horizontal bridging members.
 10. The supporting system of claim 9wherein the steel plate has a hole formed therein.
 11. The supportingsystem of claim 10 wherein each bridging is adapted to be snapped inplace.
 12. The supporting system of claim 1 wherein the bridging holesare a plurality of spaced apart bridging holes.
 13. The supportingsystem of claim 3 wherein the bridging holes are a plurality of spacedapart bridging holes.
 14. The supporting system of claim 2 wherein theupper chord and lower chord each include at least one inner flange andthe bridging holes are formed in the inner flanges.
 15. The supportingsystem of claim 14 wherein the bridging holes are a plurality of spacedapart bridging holes.
 16. The supporting system of claim 1 wherein thesupporting system includes a plurality of joists and a plurality ofbridging members.
 17. The supporting system of claim 1 wherein thebridging members include an upper bridging member and a lower bridgingmember.
 18. The supporting system of claim 17 wherein the bridgingmembers are generally L-shaped.